Compression fittings are used in industrial systems to join various sections of fluid pathways together, for example to fluidly connect two separate tubes or pipes together. FIG. 1A shows a typical union compression fitting 20 including a left nut 22 and a right nut 24 attached to a body 26 to fluidly connect a left tube 28 with a right tube 30. The left side of the union compression fitting 20, shown in cross-section in FIG. 1C, illustrates the position of the left nut 22 prior to assembly. The right side of the union compression fitting 20 shows the position of the right nut 24 after makeup.
Often compression fittings employ a ferrule assembly to prevent leakage of hydraulic fluid. As shown in FIG. 1C, the union compression fitting may include a ferrule assembly, such as a single ferrule 32 or a dual ferrule assembly (not shown), for sealing against an outer surface of the tube 28 after makeup of the left nut 22. In short, the left nut 22 is threaded onto the body 26, and as the left nut 22 advances the ferrule 32 is pressed against the body 26. The geometry of the body 26 causes a radially inward compression of the ferrule 32 onto the outer surface of the tube 28. The right nut 24 (FIG. 1A) may be madeup in a similar fashion as the left nut 22, and a ferrule assembly (not shown) similar to the ferrule 32 may seal against an outer surface of the tube 30 upon makeup of the right nut 24. Typical makeup of fittings such as this requires advancing the nut 1¼ turns (or more) from the finger tight position. This usually requires marking the nut and body position or counting hex flats to insure proper initial assembly.